THE USE OF GAMMA RAY BACK SCATTER APPARATUS TO MEASURE THIN LAYERS

DISCUSSES RELIABLE ASSESSMENT OF REPRODUCIBILITY OF MEASUREMENTS AND UNDERSTANDING OF DEPTH-SAMPLING CHARACTERISTICS OF THE APPARATUS WHEN IT IS USED FOR MEASURING /A/ DENSITY CHANGES IN A THIN LAYER COMPACTION, /B/ POINT TO POINT VARIATION OF DENSITY ACROSS THE SURFACE OF A LAYER AFTER COMPACTION. PROVIDED THE INSTRUMENT HAS BEEN DESIGNED TO MEASURE THE ABSORPTION OF BACK SCATTER OF GAMMA RADIATION, THE DENSITY DETERMINED IN THE PRESENCE OF SMALL DENSITY GRADIENTS WILL BE THE AVERAGE DENSITY OF THE LAYER LYING ABOVE THE MEAN DEPTH. THE DERIVED DENSITY OF THIS SHALLOW LAYER MAY BE SLIGHTLY ERRATIC DUE TO LAYERS OF DIFFERENT DENSITY AT DEPTHS BETWEEN 1 AND 3 TIMES THE MEAN DEPTH TO WHICH THE RAYS PENETRATE. ON SOME INSTRUMENTS ALLOWANCES CAN BE MADE FOR SUCH ERRORS. FOR A PARTICULAR APPARATUS WITH RA 226, MEAN DEPTH OF PENETRATION WAS 1.2 TO 1.8 IN FOR MATERIALS WITH DENSITY 150 TO 100 LB/SQ FT AND IT WAS USEFUL FOR STUDYING COMPACTION OF 2 1/2 IN ASPHALT BASE COURSE. /RRL/

• Supplemental Notes:
  • Vol Ln, No 730, 13PP, 8FIG, 9TAB, 4REF
• Corporate Authors:

  Road Research Laboratory /UK

  ,    
• Authors:
  • HARLAND, D G
• Publication Date: 1965-1

Subject/Index Terms

• TRT Terms: Absorption; Asphalt; Backscattering; Base course (Pavements); Bituminous mixtures; Compaction; Density; Depth; Gamma rays; Measurement; Nondestructive tests; Sampling; Surface course (Pavements); Surfacing; Tests
• Old TRIS Terms: Backscatter; Bitumen mix; Density measurement
• Subject Areas: Geotechnology; Highways; Materials;

Filing Info

• Accession Number: 00216025
• Record Type: Publication
• Source Agency: Road Research Laboratory /UK
• Files: TRIS
• Created Date: Jan 20 1994 12:00AM